Intensity-Dependent Dispersion in Nonlinear Phononic Layered Systems

2011 ◽  
Author(s):  
Kevin L. Manktelow ◽  
Michael J. Leamy ◽  
Massimo Ruzzene
Keyword(s):  
Discrete Systems ◽  
Dispersion Analysis ◽  
Constitutive Relationship ◽  
Analysis Tool ◽  
Governing Equations ◽  
Cubic Nonlinearity ◽  
Layered Systems ◽  
Element Discretization ◽  
Adequate Representation ◽  
Intensity Wave

Phononic crystals are typically considered to operate in regimes where a linear constitutive relationship provides an adequate representation. For high intensity wave propagation, however, weak nonlinearities can affect performance. For example, a cubic nonlinearity gives rise to frequency shifting and thus a shift in band gap location. In the study of nonlinear optics, a cubic term has been treated using a quasi-linear constitutive relationship with intensity dependent properties. This technique is explored herein for generating nonlinear dispersion relationships for the elastic case. In addition, a perturbation method developed previously for discrete systems, used in conjunction with a finite element discretization, is proposed as an alternative dispersion analysis tool. Simulations of the fully nonlinear governing equations are provided as validation of the predicted dispersion curves.

3D Eddy Current Testing by FEM for Detection of Crack’s in Materials

2016 ◽  
Vol 703 ◽  
pp. 349-353 ◽  
Author(s):  
Kahina Chabane ◽  
Salaheddine Harzallah ◽  
Mohamed Chabaat
Keyword(s):  
Eddy Current ◽  
Eddy Currents ◽  
Numerical Approach ◽  
Governing Equations ◽  
Finite Element Discretization ◽  
Magnetic Vector ◽  
Element Discretization ◽  
Current Testing ◽  
Micro Cracks ◽  
Set Up

In this paper, we present a nondestructive Testing by sensor Eddy current is used as a tool to control cracks and micro-cracks in materials. A new method for computing by measuring and testing related 3D Eddy currents is considered. In the process, a Potential Magnetic Vector is provided on the basis of formulations taken from the theoretical set up. Thus, results of relevant applications are obtained to check the theory consistency. A simulation by a numerical approach using Finite element discretization of 3-D Eddy Current governing equations is employed to detect cracks and damaged zones in materials and eventually to study their propagation.

Modeling of the Two-Phase Closed Thermosyphon

1987 ◽  
Vol 109 (3) ◽  
pp. 722-730 ◽  
Author(s):  
J. G. Reed ◽  
C. L. Tien
Keyword(s):  
Steady State ◽  
Analysis Tool ◽  
Governing Equations ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Proposed Model ◽  
The Times ◽  
Steady State Solutions ◽  
Liquid And Vapor Phases

A comprehensive model is developed to predict the steady-state and transient performance of the two-phase closed thermosyphon. One-dimensional governing equations for the liquid and vapor phases are developed using available correlations to specify the shear stress and heat transfer coefficients. Steady-state solutions agree well with thermosyphon flooding data from several sources and with film thickness data obtained in the present investigation. While no data are available with which to compare the transient analysis, the results indicate that, for most systems, the governing time scale for system transients is the film residence time, which is typically much longer than the times required for viscous and thermal diffusion through the film. The proposed model offers a versatile and comprehensive analysis tool which is relatively simple.

On a New Model Reduction Method for CFD Systems Used for Flow Control Design

2013 ◽  
Vol 332 ◽  
pp. 9-14
Author(s):  
Adrian Mihail Stoica ◽  
Marius Stoia-Djeska
Keyword(s):  
Model Reduction ◽  
Flow Simulation ◽  
Type Systems ◽  
Discrete Systems ◽  
Navier Stokes ◽  
Governing Equations ◽  
Flow Solver ◽  
Efficient Control ◽  
Flow Domain ◽  
External Flows

The use of active control to get better characteristics of unsteady internal and external flows is the ultimate goal of the research presented in this paper. Usually, unsteady flows are calculated using Euler and/or Navier-Stokes solvers. The efficiency of numerical simulation of an unsteady flow dramatically increases if the unsteady solution is a small perturbation about a steady-state flow, due to disturbances occurring at the boundaries of the flow domain. The main difficulty related to the flow simulation is that any CFD (Computational Fluid Dynamics) technique generates discrete systems with a very large number of states. In order to design an efficient control, the flow solver must be not only accurate and numerically effective, but also it must have a low number of states. The aim of this paper is to present a new method for model reduction of CFD systems using representative governing equations. The focus is on descriptor type systems resulting from the spatial discretization of the CFD governing equations.

Diffuse-interface modelling of thermocapillary flow instabilities in a Hele-Shaw cell

2001 ◽  
Vol 434 ◽  
pp. 153-166 ◽  
Author(s):  
M. VERSCHUEREN ◽  
F. N. VAN DE VOSSE ◽  
H. E. H. MEIJER
Keyword(s):  
Marangoni Convection ◽  
Spectral Element ◽  
Flow Instabilities ◽  
Diffuse Interface ◽  
Interface Model ◽  
Governing Equations ◽  
Diffuse Interface Model ◽  
Element Discretization ◽  
Fixed Interface ◽  
Hele Shaw Cell

In this paper we present the results of a diffuse-interface model for thermocapillary or Marangoni flow in a Hele-Shaw cell. We use a Galerkin-type spectral element discretization, based on Gauss–Lobatto quadrature, for numerical implementation of the governing equations resulting from the diffuse-interface model. The results are compared to classical results for a linear and circular fixed interface. It is found that the diffuse-interface solution converges to the classical solution in the sharp-interface limit. The results are sufficiently accurate if the interfacial thickness is only small compared to the size of the thermocapillary boundary layer, even if the interfacial thickness used is much larger than the real interfacial thickness. We also consider freely movable interfaces with a temperature gradient perpendicular to the interface. It will be shown that this situation can lead to a destabilizing Marangoni convection.

On the Main Flow Pattern in Hydrocyclones

1993 ◽  
Vol 115 (1) ◽  
pp. 21-25 ◽  
Author(s):  
C. C. Hwang ◽  
H. Q. Shen ◽  
G. Zhu ◽  
M. M. Khonsari
Keyword(s):  
Theoretical Model ◽  
Flow Field ◽  
Closed Form ◽  
Flow Pattern ◽  
Main Flow ◽  
Experimental Measurements ◽  
Main Body ◽  
Governing Equations ◽  
Adequate Representation ◽  
Good Agreement

A theoretical model is developed for the prediction of the main flow pattern in hydrocyclones. The model regards the main body of the cyclone as inviscid and includes provisions for the fluid underflow in cyclones. The governing equations are solved analytically in closed form. To verify the results, a laboratory-scale conically-shaped hydrocyclone was designed, built, and tested. Experimental measurements for axial and tangential velocities are presented with a series of tests solely devoted to the effect of underflow. The theoretical and experimental results are shown to be in good agreement. It is concluded that such an inviscid model gives an adequate representation of the main flow field in a cyclone.

scholarly journals Tool for analysis of multichannel analysis of surface waves (MASW) field data and evaluation of shear wave velocity profiles of soils

2018 ◽  
Vol 55 (2) ◽  
pp. 217-233 ◽  
Author(s):  
Elin Asta Olafsdottir ◽  
Sigurdur Erlingsson ◽  
Bjarni Bessason
Keyword(s):  
Surface Waves ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Profiles ◽  
Dispersion Analysis ◽  
Silty Sand ◽  
Analysis Tool ◽  
Multichannel Analysis ◽  
Inversion Analysis

Multichannel analysis of surface waves (MASW) is a fast, low-cost, and environmentally friendly technique to estimate shear wave velocity profiles of soil sites. This paper introduces a new open-source software, MASWaves, for processing and analysing multichannel surface wave records using the MASW method. The software consists of two main parts: a dispersion analysis tool (MASWaves Dispersion) and an inversion analysis tool (MASWaves Inversion). The performance of the dispersion analysis tool is validated by comparison with results obtained by the Geopsy software package. Verification of the inversion analysis tool is carried out by comparison with results obtained by the software WinSASW and theoretical dispersion curves presented in the literature. Results of MASW field tests conducted at three sites in south Iceland are presented to demonstrate the performance and robustness of the new software. The soils at the three test sites ranged from loose sand to cemented silty sand. In addition, at one site, the results of existing spectral analysis of surface waves (SASW) measurements were compared with the results obtained by MASWaves.

Energy Dispersion Analysis Tool

2014 ◽  
pp. 599-605
Author(s):  
Athula Kulatunga ◽  
Edward R. Winter ◽  
John Piller
Keyword(s):  
Dispersion Analysis ◽  
Analysis Tool ◽  
Energy Dispersion

A Parametric Study of the Accuracy of Several Radiative Transport Solution Methods for a Set of 2-D Benchmark Problems

2013 ◽  
Author(s):  
John Tencer ◽  
John R. Howell
Keyword(s):  
Radiation Transport ◽  
Benchmark Problems ◽  
Discrete Ordinates ◽  
Test Problems ◽  
Governing Equations ◽  
Element Discretization ◽  
Discontinuous Boundary ◽  
All Solutions ◽  
Solution Methods ◽  
Ray Effects

Several of the most popular deterministic radiation transport methods for heat transfer are compared. Relative solution error is compared as a function of optical thickness and scattering albedo. The test problems are chosen to represent a range of problem types. Problems with discontinuous boundary conditions are included to evaluate ‘ray effects’ for discrete ordinates solutions. A brief derivation and a statement of the governing equations for each method is included so that the details of the precise method used is clear. All solutions are generated using finite element discretization. Where applicable, any stabilization used is included in the statement of the governing equations.

Linear Visco-Resistive Computations of Magnetohydrodynamic Waves: I. The Code and Test Cases

1994 ◽  
Vol 144 ◽  
pp. 503-505
Author(s):  
R. Erdélyi ◽  
M. Goossens ◽  
S. Poedts
Keyword(s):  
Resonant Absorption ◽  
Numerical Code ◽  
Mhd Waves ◽  
Test Cases ◽  
Numerical Accuracy ◽  
Element Discretization ◽  
Flux Tubes ◽  
Magnetohydrodynamic Waves ◽  
Viscosity Coefficients ◽  
Magnetic Flux Tubes

AbstractThe stationary state of resonant absorption of linear, MHD waves in cylindrical magnetic flux tubes is studied in viscous, compressible MHD with a numerical code using finite element discretization. The full viscosity tensor with the five viscosity coefficients as given by Braginskii is included in the analysis. Our computations reproduce the absorption rates obtained by Lou in scalar viscous MHD and Goossens and Poedts in resistive MHD, which guarantee the numerical accuracy of the tensorial viscous MHD code.

Ethnogeriatrics: Development and Application of the Cohort Analysis Tool

2014 ◽  
Vol 21 (2) ◽  
pp. 37-52
Author(s):  
Melen McBride
Keyword(s):  
Healthcare Professionals ◽  
Cohort Analysis ◽  
Analysis Tool ◽  
Speech Language Pathology ◽  
Clinical Tool ◽  
Research Activities ◽  
Key Concepts ◽  
Practice Teaching ◽  
Language Pathology ◽  
Significant Factors

Ethnogeriatrics is an evolving specialty in geriatric care that focuses on the health and aging issues in the context of culture for older adults from diverse ethnic backgrounds. This article is an introduction to ethnogeriatrics for healthcare professionals including speech-language pathologists (SLPs). This article focuses on significant factors that contributed to the development of ethnogeriatrics, definitions of some key concepts in ethnogeriatrics, introduces cohort analysis as a teaching and clinical tool, and presents applications for speech-language pathology with recommendations for use of cohort analysis in practice, teaching, and research activities.

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